The epiphyseal closure profile, and x-ray method for determining full skeletal maturity and intermediate stages of skeletal maturity in dogs is being refined. A critical length for bone reconstitution of a complete osteal-periosteal discontinuity, in the mid-shaft of the radius of skeletally mature dogs with rigid internal plate and screw fixation, between 1 mm. and 10 mm. in length is being determined: that is, a discontinuity just long enough to obviate spontaneous bone healing. Exogenous hormones will be administered to otherwise physiologically intact skeletally mature dogs with surgically created critical length radial discontinuities to determine their effect on stimulation of bone formation in the discontinuity site to re-establish bone continuity of the radius.